FIG. 1 is a cross sectional view of general laminated ceramic capacitor 11 formed by using a dielectric ceramic composition. With reference to FIG. 1, laminated ceramic capacitor 11 is configured by electrically connecting inner electrodes 13 and 14 respectively to a pair of outer electrodes 18 and 19 formed on both opposed end faces 16 and 17 of sintered body 15. Then, this sintered body 15 is formed by sintering a laminated body formed by laminating a plurality of inner electrodes 13 and 14 alternatively by sandwiching a ceramic sheet formed in a sheet form which becomes dielectric layer 12 that is the dielectric ceramic composition after sintering and by laminating protective layers 20 top and bottom.
Then, an expensive precious metal is used in inner electrodes 13 and 14 and outer electrodes 18 and 19 in general to prevent a reaction with dielectric layer 12 at sintering. However, substitution has recently proceeded from an expensive precious metal to an inexpensive base metal such as nickel (Ni).
A conventional manufacturing method is explained below on laminated ceramic capacitor 11 configured as above.
First, a laminated body (not shown) is obtained by laminating alternatively a plurality of layers of a ceramic sheet that is an origin to be dielectric layer 12 after sintering and an electrode paste containing a base metal material such as Ni to be inner electrodes 13 and 14 after sintering, laminating protective layers 20 on this top layer and bottom layer, and pressure-bonding. Then, after cutting this laminated body into a chip shape with a prescribed size, sintering is performed at a prescribed temperature. At this time, sintered body 15 is formed by performing sintering in a reduced atmosphere such as a nitrogen gas atmosphere to prevent oxidative deterioration of inner electrodes 13 and 14.
Then, an external electrode paste comprising a base metal material is applied onto both end faces 16 and 17 of sintered body 15 where inner electrodes 13 and 14 are exposed, and baking is performed in a reduced atmosphere such as a nitrogen gas atmosphere so that external electrodes 18 and 19 do not oxidatively deteriorate.
Japanese Patent Unexamined Publication No. 61-155255 is known for example as prior technical document information relating to a dielectric ceramic composition suppressing reduction deterioration at such sintering of dielectric layer 12.
However, a laminated ceramic capacitor using the dielectric ceramic composition shown in Japanese Patent Unexamined Publication No. 61-155255 has large deterioration of the insulation resistance lifetime characteristic (IR lifetime characteristic). In addition, ensuring of reliability becomes more difficult as dielectric layer 12 becomes thinner and it has a problem that the temperature variation rate of capacitance becomes large. Furthermore, when copper (Cu) that is easy to generate a solid solution with Ni of inner electrodes 13 and 14 is selected as external electrodes 18 and 19 and it is baked to sintered body 15 in a reduced atmosphere, dielectric layer 12 is reduced and there is a problem that insulation resistance of the laminated ceramic capacitor becomes small.